Conventionally, as an apparatus that extracts energy from combustion gas generated by burning fuel, there is a gas turbine in which a turbine is rotated by using energy of the combustion gas generated by burning fuel and rotation energy is output from a rotor.
For example, Patent Document 1 discloses a technique in which a valve is installed for supplying external air into an upper cylinder casing, and at the time of suspending an operation of the gas turbine, the external air is introduced from the upper cylinder casing into a cylinder casing to cool the upper cylinder casing, thereby preventing thermal deformation of the cylinder casing.
Patent Document 1: Japanese Patent Application Laid-open No. 2006-37855